Conventionally, an electronic circuit connected to a resonator of a MEMS type resonator device can also be used to perform an angular velocity measurement. An angular velocity may be measured on one, two or three axes, for example with a MEMS type gyroscope. The gyroscope generally includes at least one mass maintained by a structure in the form of a spring and capable of being set in oscillation electrically at a frequency determined by the spring constant with a defined damping factor for the mass. An angular velocity can be determined on the basis of the oscillation velocity of the mass and the force generated, which is perpendicular to the angular velocity and to the oscillation motion of the mass.
To achieve this, there exist electronic drive circuits, which preferably use oscillation in a phase lock loop to drive oscillation along at least one axis of motion of the MEMS resonator as described, in particular, in EP Patent Application Nos 2 259 019 A1 and 2 336 717 A1. The use of a phase lock loop for maintaining the oscillation of the resonator mass does not reduce the general power consumption of the system for controlling the oscillation phase and amplitude, which is a drawback. Account must also be taken of a relatively high supply voltage for maintaining the oscillation of said mass, which does not allow the start time of the gyroscope drive circuit to be reduced, which are further drawbacks.
The electronic drive circuit of a MEMS gyroscope resonator on one, two or three axes may also be cited, which is disclosed in the thesis entitled “System and circuit design for a capacitive MEMS gyroscope” by Mikko Saukoski of Helsinki University of Technology, Faculty of Electronics, Communication and Automation, Department of Micro and Nano Sciences dated 2008 (ISBN9789512292974). As previously, a phase lock loop is used for maintaining the oscillation of the mass of the primary resonator of the gyroscope, as shown in FIG. 2.9 of page 31. The rotational velocity measurement is determined by the secondary resonator of the gyroscope in a direction perpendicular to the motion of the oscillating mass. This does not reduce the electrical power consumption of the system, which is a drawback. Several disruptions are also noted between actuation of the mass oscillation and detection of the mass motion for regulating the oscillation amplitude, which is another drawback.
The document entitled “Force to rebalance control of HRG and suppression of its errors on the basis of FPGA” by Xu Wang, Wenqi Wu, Bing Luo, Zhen Fang, Yun Li and Qingan Jiang, published on 16 Dec. 2011 in Sensors 2011 (ISSN 1424-8220), may also be cited. This document discloses a new concept of adapting force for a hemisphere gyroscopic resonator on the basis of an FPGA. The system disclosed provides for forced oscillation of the mass by a VCO oscillator on the basis of cos(ω·t) and sin(ω·t) signals. The system detects the motion of the secondary resonator, which is defined as the south electrode for powering the primary resonator, which is defined as the west electrode. This therefore cancels out vibration on the primary. In this control loop, phase and amplitude are controlled to supply exactly the power necessary to cancel out the motion of the secondary.
One drawback of this system is that it uses a VCO oscillator. This makes it impossible to reduce the general electrical power consumption of the system for controlling oscillation phase and amplitude. Further, the information from the secondary is used to oscillate the primary resonator. This complicates manufacture, and also the precision of the oscillation phase and amplitude control. The primary is dependent on the secondary, which is another drawback.